This invention relates generally to mattress foundation structures and more particularly to a box spring assembly of a type which utilizes non-coil springs. Box spring assemblies of this general type have been known since 1964, the first such spring assembly being disclosed in U.S. Pat. No. 3,286,281. Subsequently issued patents disclosing the same general type of box spring assemblies are: U.S. Pat. Nos. 3,487,480; 3,506,987; 3,574,240; 3,574,241; 3,665,529; 3,620,157; 3,755,833; 3,824,639; 3,852,838; 4,060,862; 4,120,058; 4,131,961; 4,195,376; 4,218,790; 4,238,861; 4,251,892; 4,253,208; 4,339,834; 4,371,152; 4,398,705; 4,470,584; 4,452,438; and 4,739,977.
Box spring assemblies of the general type shown in the above list of patents all of which are owned by the assignee of this application, are advantageous with respect to the conventional box spring assemblies using coil springs because they provided as desired stiffer foundation for the mattress and contain a reduced amount of wire. These box spring assemblies are also advantageous from the standpoint of prolonged service life, ease of assembly, and cost of manufacture.
Additional box spring assemblies of this general type are shown in U.S. Pat. Nos. 3,546,723; 3,596,299; 3,722,013; 3,825,960; 3,833,948; 3,835,485; 3,869,740; 3,990,121; and 4,000,531.
The above list of patents utilize springs made of formed spring wire having various torsion bar arrangements. The present invention replaces one of these torsion bar portions with a coil spring portion to evenly distribute torsional stresses under working and impact loads. The present invention further utilizes limited deflection wire columns to prevent total collapse of the box spring and to provide improved shock resistance.
The box spring according to the present invention includes a generally horizontal rectangular frame and a horizontal mattress support deck disposed a predetermined distance above the frame. The deck includes straight deck wires arranged in a crisscross fashion, some of which extend lengthwise of the frame and others which extend crosswise. Bounding the crisscrossed deck wires is a border wire located in the same plane as the deck wires and substantially vertically aligned with the frame below.
Between the mattress support deck and the frame are a plurality of deck support springs which yieldably support the deck on the frame. Each spring has a deck attaching portion attached to the deck wires with clips in a conventional manner and a pair of vertically yieldable portions connected between the deck and the frame. The vertically yieldable portion has a vertically spiraling coil spring portion in series with an upright column portion and a foot portion. The coil spring portion is connected between the attaching portion and the upright column portion which joins the coil spring portion with the foot portion.
The combination of a coil spring with the wire column results in a box spring assembly having softer firmness, feel and floatation characteristics than those attainable in a box spring assembly utilizing only torsion bar springs. The result is an improved box spring assembly having the increased shock resistance characteristic of a limited deflection column and the firmness and floatation characteristics of a coil spring assembly.
Further objects, features, and advantages of this invention will become apparent from a consideration of the following description, the appended claims, and the accompanying drawing.